. Railway track and track work . plate being kept from slacking 104 TRACK. loose by split keys driven through slots in the bolts. The Pittsbnrg joint hasangle splice bars with the flange on top, and outside of these are drop-forgedsplice bars, a channel-shaped strip of fiber lying against the inner bar and base ofrail. The outer bars are of channel section, thicker at the middle than at theends, and matle solid at the bolt holes so as to require long bolts. Each bolt hasa flanged bushing on each end, with a metal washer between the flange and tliehead or nut. Expansion Joints.—With continuous
. Railway track and track work . plate being kept from slacking 104 TRACK. loose by split keys driven through slots in the bolts. The Pittsbnrg joint hasangle splice bars with the flange on top, and outside of these are drop-forgedsplice bars, a channel-shaped strip of fiber lying against the inner bar and base ofrail. The outer bars are of channel section, thicker at the middle than at theends, and matle solid at the bolt holes so as to require long bolts. Each bolt hasa flanged bushing on each end, with a metal washer between the flange and tliehead or nut. Expansion Joints.—With continuous rails and where creeping cannot bechecked, expansion joints must be provided at intervals, and these are usuallymade with switch points. On long-span steel bridges some special joint must beused to allow for the movement at the expansion joint in the structure. Theseusually have the rails lapped or scarfed, so as to maintain a continuous rail whileallowing for sufficient longitudinal motion in the adjacent rails. Fig. 46 shows. -W—^^ Elevation. Section C-D. Fls- ^G-—xpansion Rail Joint; Poughkeepsie Bridge. the form used on the Poughkeej^sie bridge, which provides for several inches ofmovement. A heavy base plate and upi:)er packing plates form a trough inwhich the rail ends slide, the rails being halved for a length of 12 ins. Neitherrail has its web cut. On the gage side of the rail the line is made perfect by plan-ing off from the inside of the head an amount equal to the thickness of the web,the rail being sligiitly bent beyond the joint so as to permit this. The other railis left of its original thickness. At the ends of the four anchor arms of the Thebescantilever britige, the rails do not lap, but have their ends 7 ins. apart. Wheelsare carried across the gap by carrier or bridge rails laid against the outside of thetrack rails and bolted to one of them. The outside face of the rail head is planedaway to a width of 25/32-in. for a length of IS ins. on the fixed end
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